The problem of creation of improved conditions for cattle oocyte maturation in vitro was studied in the Republic of Belarus. The objects of study were cattle oocytes and embryos of early preimplantation stages of development obtained in vitro conditions. Research results showed that application of bovine serum in complex with embryonic or fetal serum in the process of oocyte cultivation in vitro conditions made it possible to obtain 35,5-44,8% of breaking down cells and 16,1-17,2 % of embryos at the stage of morula-blastocyte. Entering of 0,02 ng/ml of gonadotropin-releasing hormone (Surfagon) into media for oocyte maturation at the cost of regulation of the processes of growing and development of oocyte-cumulus complexes made it possible to increase of yield of matured till the stage of metaphase II oocytes up to 89,3 %. At the same time, the yield of divided embryos after fertilization increased on 2,5 % in comparison with control indexes and amounted 45,2 %. Research results showed that the synthetic phytohormone epibrassinolide could be used as a biologically active factor in the process of getting early embryos in vitro in concentration of 2 x 10E-7 – 2 x 10E-9 mole/l. It made it possible to get 46,4-55,0 % of divided cells and 14,2-16,2% preimplantation embryos

Efficiency of cultivation of cow preimplantation embryos and support of pluripotent properties in different nutritive media was analyzed; a method of getting early embryos in vitro for the genetically engineered purposes was developed in the conditions of the Republic of Belarus. Oocyte separation was realized in 3; 3-6; 6-9; and 9-12 hours after ovariectomy for the studying of the influence of storage period of ovaries on the output qualitative embryos. Oocyte separation was realized by bisection with adding of 1% of fetal cattle serum, 10 units/ml of gentamicin and 1 unit/ml of heparin. Oocyte-cumulus complexes maturing took place in CO2-bath with 5% of CO2 in atmosphere of maximum humidity and temperature of 38 deg C in TS-199 (Sigma) media with entering of 25 mM/l of buffer Hepes, 10 unit/ml of gentamicin and biologically active substance (20 % of fetal calf serum, 10 mg/ml of bovine serum albumin and 5 % of estrous cow serum with 10 mg/ml of bovine serum albumin). Research result showed that application of 10 mg/ml of bovine serum albumin into TS-199 media made it possible to increase the yield of cattle embryos at the preimplantation stages in vitro conditions on 19,1%, as well as to increase the fetal calf serum in quantity 15% to the nutritive media volume up to 16,0 %. Application of sodium pyruvate and calcium lactate in the process of cultivation of early cattle embryos obtained in vitro conditions made it possible to increase the yield of preimplantation embryos on 5,4 %. Specifically, the level of transformation of morulas into blastocysts was 44,4 %